1. Field of the Invention
The invention is related to a fiber optical polishing machine to polish end surfaces of optical fibers secured in ferrules, or the connection end surfaces of optical connectors with high polishing quality.
2. Description of Related Art
Unlike electrical wires, optical fibers require end-surface treatment for proper light propagation. The two most common ways of end surface preparations are cleaving and polishing, in which polishing is essential and key process for almost all glass-based fibers with cladding diameters larger than 200 microns. Furthermore, polishing is required for all fiber connectors used in optical communication to get smaller insertion loss and higher return loss. Because the diameter of most optical fibers ranges from 80 um to 1000 um, too small to be polished directly, ceramic, metal, or glass ferrules are often used to protect the fibers. The most commonly used fiber connectors employ ceramic or metal ferrules. Glass ferrules are preferred when optical coating is necessary after polishing for better adhesion. Unlike lens polishing, the convex surfaces of the fiber ferrules are achieved by pressing the ferrules on flexible polishing pads. The domed surface is ideal for true physical contact between two single mode fiber cores. Physical contact is also possible with multimode fibers when the core diameter is small. The dome radius of curvature is determined by the polishing locus (movement path), pressing force, the hardness and the thickness of the polishing pad. A true physical contact also requires a slight undercut of the fiber. The amount of undercut is the result of the type of polishing film used, polishing locus, the force applied, and the polishing speed. As one can imagine, a consistent high-quality and high speed polish can only be achieved by a polishing machine with a well designed polishing locus.
U.S. Pat. No. 6,190,239 illustrates a polishing method using two stage members to create and maintain a figure eight polishing path pattern for polishing machine. The specific embodiment disclosed includes two server motors, motor drivers and a computer program that controls the method.
U.S. Pat. No. 4,831,784 discloses an apparatus for fiber polishing machine. The fibers are mounted on a jig so that their end faces are pressed against a polishing film attached to a rotary disk. The jig performs an orbital motion while describing a relatively small circle, and the polishing disc is turned in a large circle. The polishing path pattern is a cycloid curve. However, the device is not without its problems. That is, since its polishing disc only turns around on its axis and the component supporting the optical fiber makes a movement corresponding to the revolution, the polishing quality fluctuates depending on the mounting position of the optical fiber. Besides, fiber movement during polishing process is not allowed for larger quantity fiber polishing.
Another U.S. Pat. No. 4,979,334 by Takahashi, discloses a polishing disk, supporting a polishing medium, wherein the polishing disk is made to rotate around its own axis while revolving about another axis by a rotating motor, a revolving motor and a complex mechanical mechanism. While this machine produces a better polishing effect by the combined rotating and revolving motion, but one of the drawback is to use two electric motors.
U.S. Pat. No. 6,736,702 developed a more complex gear transmission system realizing the similar polishing trace as U.S. Pat. No. 4,979,334. But it still requires two electric motors to drive the polishing machine.
In some applications of fiber communication such as oil and gas field, where electrical and other powers are not allowed for fire prevention, a manual fiber optic polisher is the only option. In other outdoor applications, where power is not available and/or battery is depleted, a manual polisher comes in extremely handy. However, the prior arts, or the existing fiber optic polishing machine on the market can not be turned into a manual polisher because they all require two motors for driving. In other words, their mechanical transmission systems have two degree-of-freedom (DOF).